package com.itheima.Servlet.验证码;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/checkCode")
public class CheckCode  extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //服务器通知浏览器不要缓存
        resp.setHeader("pragma","no-cache");
        resp.setHeader("cache-control","no-cache");
        resp.setHeader("expires","0");

        //在内存中创建一个长80，宽30的图片，默认黑色背景
        //参数一：长
        //参数二：宽
        //参数三：颜色
        int width = 80;
        int height = 30;
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);

        //获取画笔
        Graphics g = image.getGraphics();
        //设置画笔颜色为灰色
        g.setColor(Color.GRAY);
        //填充图片
        g.fillRect(0,0, width,height);

     /*第一步*/   //产生4个随机验证码，12Ey
        String checkCode = getCheckCode();
        System.out.println("checkCode = " + checkCode);
        //使用session 会话域
        req.getSession().setAttribute("checkCode",checkCode);


        //设置画笔颜色为黄色
        g.setColor(Color.YELLOW);
        //设置字体的小大
        g.setFont(new Font("黑体",Font.BOLD,24));
        //向图片上写入验证码
        g.drawString(checkCode,15,25);

        //将内存中的图片输出到浏览器
        //参数一：图片对象
        //参数二：图片的格式，如PNG,JPG,GIF
        //参数三：图片输出到哪里去
        ImageIO.write(image,"PNG",resp.getOutputStream());
    }
    /**
     * 产生4位随机字符串
     */
    private String getCheckCode() {
        String base = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefg";
        Random r = new Random();
        StringBuffer sb = new StringBuffer();
        for(int i=1;i<=4;i++){
            //产生0到size-1的随机值
            int index = r.nextInt(base.length());
            //在base字符串中获取下标为index的字符
            char c = base.charAt(index);
            //将c放入到StringBuffer中去
            sb.append(c);
        }
        return sb.toString();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req,resp);
    }
}
